Mobile electronic devices, such as smartphones, tablets, and smartwatches are in wide use in the world today. Such electronic devices typically employ a touch sensitive display for both data display as well as to receive user input. Most of these touch sensitive displays utilize capacitive touch sensing.
A typical touch sensitive display includes a display layer constructed from technology such as LCD, IPS, or AMOLED, as well as a sensing layer. A transparent layer is adjacent to and spaced apart from the display layer. A typical sensing layer includes a plurality of parallel drive lines, and a plurality of parallel sensing lines. The sensing lines capacitively intersect the drive lines. In operation, a single drive line is driven with a wave, such as a square wave or sine wave. The capacitance between the sensing lines and the driven drive line is sensed at the point where they intersect. Presence of a human finger or a conductive object alters the expected capacitance at the intersection point, and by measuring the change in capacitance, a touch between the finger or conductive object and the touch sensitive display can be detected.
Such conductive objects may include styluses, which are typically cylindrical objects with a point. Where a stylus presents a similar footprint on the touch sensitive display as a fingertip, routines similar or the same as those used to make accurate determinations from the measured capacitance changes due to fingertip touches may be used. However, where a stylus presents a somewhat smaller to substantially smaller footprint on the touch display when compared to a fingertip, routines used to make determinations from the measured capacitances due to fingertip touches may lead to inaccurate results. Routines more sensitive to smaller stylus tips exist, but those may incorrectly detect a finger hover instead of, or in addition to, the stylus tip.
Therefore, further techniques in the area of processing capacitance change data collected by touch sensitive displays from touches made by small styluses are needed.